The gradient antialias could leave a half-covered pixel where an opaque source reaches h = 1. Add an endpoint guard on CPU and GPU and cover an opaque edge in the regression test.
CC Environment now fades nearly transparent environment texels to black continuously
(colour / max(alpha, 1e-3)) instead of a hard 1e-6 un-premultiply cut-off, which turned the
filtered map's float noise into colour.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>